US20050268736A1 - Mechanical actuator including a helical-cam nut - Google Patents

Mechanical actuator including a helical-cam nut Download PDF

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Publication number
US20050268736A1
US20050268736A1 US10/524,298 US52429805A US2005268736A1 US 20050268736 A1 US20050268736 A1 US 20050268736A1 US 52429805 A US52429805 A US 52429805A US 2005268736 A1 US2005268736 A1 US 2005268736A1
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Prior art keywords
ball
tubular body
nut
balls
helical
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Abandoned
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US10/524,298
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English (en)
Inventor
Jean-Pierre Gaechter
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INNOVATION TECHNOLOGIE CONSEIL A RESPONSABILITE Ltee Ste
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Bubendorff SA
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Application filed by Bubendorff SA filed Critical Bubendorff SA
Assigned to BUBENDORFF reassignment BUBENDORFF ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: GAECHTER, JEAN-PIERRE
Publication of US20050268736A1 publication Critical patent/US20050268736A1/en
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Assigned to GAECHTER, JEAN-PIERRE reassignment GAECHTER, JEAN-PIERRE ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BUBENDORFF
Abandoned legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
    • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
    • F16H25/20—Screw mechanisms
    • F16H25/22—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members
    • F16H25/2204—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members with balls
    • F16H25/2209—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members with balls with arrangements for taking up backlash
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
    • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
    • F16H25/20—Screw mechanisms
    • F16H25/22—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members
    • F16H25/2204—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members with balls
    • F16H25/2214—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members with balls with elements for guiding the circulating balls
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
    • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
    • F16H25/20—Screw mechanisms
    • F16H25/22—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members
    • F16H25/2204—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members with balls
    • F16H25/2214—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members with balls with elements for guiding the circulating balls
    • F16H25/2228—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members with balls with elements for guiding the circulating balls the device for circulation forming a part of the screw member
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
    • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
    • F16H25/20—Screw mechanisms
    • F16H25/24—Elements essential to such mechanisms, e.g. screws, nuts
    • F16H25/2427—Elements essential to such mechanisms, e.g. screws, nuts one of the threads being replaced by a wire or stripmetal, e.g. spring
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
    • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
    • F16H25/20—Screw mechanisms
    • F16H2025/2062—Arrangements for driving the actuator
    • F16H2025/2075—Coaxial drive motors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T74/00—Machine element or mechanism
    • Y10T74/18—Mechanical movements
    • Y10T74/18568—Reciprocating or oscillating to or from alternating rotary
    • Y10T74/18576—Reciprocating or oscillating to or from alternating rotary including screw and nut
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T74/00—Machine element or mechanism
    • Y10T74/18—Mechanical movements
    • Y10T74/18568—Reciprocating or oscillating to or from alternating rotary
    • Y10T74/18576—Reciprocating or oscillating to or from alternating rotary including screw and nut
    • Y10T74/18672—Plural screws in series [e.g., telescoping, etc.]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T74/00—Machine element or mechanism
    • Y10T74/19—Gearing
    • Y10T74/19642—Directly cooperating gears
    • Y10T74/19698—Spiral
    • Y10T74/19702—Screw and nut
    • Y10T74/19712—Threadless

Definitions

  • the invention relates to the field of the mechanical linear actuators and, in particular, of the mechanical actuators driven by an electric motor (electromechanical actuators).
  • electromechanical linear actuators are related to the needs in fields such as robotics and home systems. Indeed, in these fields the electromechanical jacks compete with the traditional, hydraulic or pneumatic jacks, because they are more easily controllable, more accurate and do not require an external source of fluid.
  • These electromechanical actuators generally include a ball screw on which a nut is mounted.
  • the nut is rotated by an external geared motor. The rotation of the nut drives the screw in translation.
  • An object of the invention is to provide a compact actuator structure and the manufacture of which would be simplified compared to the actuator structures of the prior art.
  • the invention provides an actuator including a first tubular body, a nut positioned inside the tubular body and having at least a generally helical ball-race, balls arranged between the ball-race and the tubular body, and driving means for rotating the nut, said driving means comprising a motor, the rotation of the nut driving the tubular body in translation with respect to the nut, characterized in that the motor is mounted fixed inside a second body capable of being displaced in translation with respect to the first tubular body.
  • the actuator comprises an internal nut allows to position the motor inside a second body.
  • the re-circulation path can be integrated into the nut.
  • This arrangement leads to a compact actuator structure the external appearance of which is similar to that of the pneumatic actuators.
  • the actuator does not leave visible any external geared motor device.
  • the actuator provided is thus particularly compact, compared to the effort which it is capable of generating.
  • tubular structure imparts to the actuator a better buckling strength than a traditional actuator having an external nut mounted about an internal screw.
  • the balls are fitted between the race and the first tubular body, with a determined radial prestressing.
  • the race includes a helical portion extending about the nut according to an angle of less than 360 degrees and a widened portion connecting the adjacent ends of the helical portion, said widened zone constituting a re-circulation zone for the balls.
  • This implementation has the advantage of not requiring the formation of an internal re-circulation race in the nut.
  • the balls are automatically “recycled” as soon as they reach the re-circulation zone.
  • the inner surface of the first tubular body can advantageously have helical ball-races the function of which is to guide the balls. These ball-races reduce the risks of sliding of the balls on the inner surface of the first body when the actuator exerts a significant effort.
  • the widened re-circulation zones allow the passing over of the balls from one ball-race to an adjacent race, over a race edge during their re-circulation.
  • the nut includes several aligned elements, of a cylindrical general shape, each having at least a bevel forming a helical cam surface, the bevels forming, two by two, helical ball-races in which balls are positioned.
  • Each element is formed from a cylindrical part with a straight cross-section, one circular edge of which is beveled, in order to form said helical cam surface inclined with respect to the axis of the cylindrical part, the ends of helical surface being joined by a setback surface with a preferably conical general shape.
  • Each element of the nut is formed from a cylindrical part with a straight cross-section, i.e. the cylindrical part is limited by two parallel planes orthogonal to its axis of rotation. This is a simple shape. The shape of the elements is therefore easier to be generated than in the prior art.
  • the setback surface can also have a general shape that is convex, concave, planar, cylindrical, planar with conical connection or cylindrical connection or the like.
  • each helical cam surface forms a setback and two elements are so positioned with respect to each other that their setbacks are in front of each other, said setbacks forming the balls re-circulation zone.
  • the prestressing exerted on the balls is generated by tightening the elements with respect to each other.
  • the actuator can include an element adjusting nut for controlling the prestressing exerted onto the balls.
  • the effort which can be exerted by the actuator directly depends on the prestressing applied to the balls and adjusted by the adjusting nut.
  • the actuator includes elastic means interposed between the adjusting nut and the nut elements through which the adjusting nut exerts prestressing on the elements.
  • the motor is an electric or hydraulic motor.
  • the invention also relates to a nut element aimed at being arranged in an actuator as defined above.
  • the nut element is formed from a cylindrical part with a straight cross-section, one circular edge of which is beveled to form said helical cam surface inclined with respect to the axis of the cylinder, the ends of the helical surface being connected by a setback surface with a conical general shape.
  • the invention also relates to a process for obtaining a nut element aimed at being arranged in an actuator according to the invention.
  • the process includes the steps consisting in machining a circular edge of a cylindrical part with a straight cross-section, in order to generate a bevel forming a helical cam surface inclined with respect to the axis of the cylinder, the ends of helical surface being connected by a setback surface with a conical general shape.
  • FIG. 1 shows a longitudinal cross-sectional view of an example of an actuator structure according to an embodiment of the invention in which the driving means include an electric motor.
  • FIG. 2 is a diagram representing a prestressed ball
  • FIG. 3 is a perspective view of a cam constituting the nut
  • FIG. 4 is a diagram representing a step of generating a helical cam surface
  • FIG. 5 is a diagram representing the positioning of two cams with respect to each other on the driving shaft of the actuator
  • FIG. 6 schematically shows the positioning of two pairs of cams with respect to each other, in which the ball re-circulation zones are regularly distributed around the driving shaft
  • FIG. 7 shows an example of inner surface of the tubular body having ball-races formed by a wire wound into a spiral
  • FIGS. 8 and 9 schematically show ball-races formed by a first wound wire and a intermediate second wire arranged between the windings of the first wire
  • FIG. 10 schematically shows ball-races formed by plastic distortion of an inner tube arranged in the tubular body
  • FIG. 11 schematically shows a step of welding of the inner tube in the tubular body
  • FIG. 12 shows a longitudinal cross-sectional view of an actuator structure of a telescopic type
  • FIG. 13 shows the actuator of FIG. 12 in unfolded position
  • FIG. 14 schematically shows the positioning of a ball resting between the nut and a ball-race
  • FIG. 15 is a cross-sectional and perspective view of the balls when they arrive in a re-circulation zone
  • FIG. 16 is a diagram representing the positioning of two cams with respect to each other.
  • the linear actuator includes an inner tube 10 and an outer tube 20 the diameter of which is larger than the diameter of the inner tube 10 .
  • the inner tube 10 extends partly in the outer tube. Both tubes 10 and 20 are locked in rotation with respect to each other and are capable of being actuated to slide with respect to each other in their longitudinal direction.
  • the actuator includes a drive mechanism including a driving shaft 30 extending according to the longitudinal axis of the tubes 10 and 20 .
  • the shaft 30 is rotated by an electric motor 2 fixed at one of its ends and positioned in the inner tube 10 .
  • the motor 2 and the shaft 30 are maintained in the inner tube 10 through a cylindrical support 3 fixed to the inner tube.
  • the shaft 30 is guided in the inner tube 10 through two ball bearings 7 and 9 the inner ring of which is fitted on the shaft 30 and the outer ring rests against the inner surface 11 of the inner tube 10 .
  • Both bearings 7 and 9 are maintained at a distance by a spacer 8 in the form of a cylindrical sleeve resting on the inner rings of the bearings 7 and 9 as well as through a spacer 12 pinned in the inner tube 10 and resting on the outer rings of the bearings 7 and 9 .
  • the absorption of the axial forces exerted on the bearings can occur either through the spacer 12 or by any other equivalent means (for example circlips locking the bearing).
  • the shaft 30 supports in addition an adjusting nut 4 , a set of Belleville washers 5 , a first clamping washer 6 positioned between the support 3 of the motor and the bearing 7 .
  • the clamping washer 6 rests on the inner cage of the bearing 7 .
  • the shaft 30 also supports a second clamping washer 1 and ball nut 70 , positioned between the bearing 9 and a thrust element 31 at the end of the shaft 30 .
  • the nut 70 is formed of a succession of cams 40 , 50 and 60 with cylindrical general shapes mounted aligned on the shaft 30 and locked in rotation with respect to the shaft by a key.
  • the cams 40 , 50 , 60 have helical bevels 41 , 51 and 52 , 62 , oriented at 45° with respect to the axis of the shaft 30 .
  • These bevels 41 , 51 , 52 , 62 form, two by two, helical ball-races in which balls 22 are positioned.
  • the balls 22 are into contact, on the one hand, with two surfaces with opposite bevels, 41 and 51 , or 52 and 62 and, on the other hand, with the smooth inner surface 21 of the outer tube 20 .
  • the radial force applied to the balls 22 is controlled by tightening the nut 4 .
  • the adjusting nut 4 applies a compressive force to the Belleville washers 5 according to the longitudinal direction of the shaft 30 .
  • This compressive force is transmitted to the cams 40 , 50 , 60 through the clamping washer 6 which transmits and distributes the clamping force on the inner cages of the bearings 7 and 9 and on the clamping washer 1 .
  • the cams 40 , 50 , 60 are thus in compressed state between the clamping washer 1 , the balls 22 and the thrust element 31 at the end of the shaft 30 .
  • the actuator of FIG. 1 includes two ball-races formed by three cams 40 , 50 and 60 aligned on the shaft 30 .
  • the force that can be exerted by the actuator of FIG. 1 directly depends on the prestressing applied to the balls and set by the adjusting nut 4 .
  • the prestressing force which can be applied to the balls 22 remains limited by the Hertz pressure which the surface of the cams 40 , 50 , 60 and the inner surface 21 of the outer tube 20 can be subjected to.
  • each ball 22 When the motor 2 of the actuator of FIG. 1 is operating, it rotates the shaft 30 and, hence, the cams 40 , 50 and 60 which are keyed on the latter. The balls 22 then roll between their ball-race and the inner surface of the outer tube.
  • the tangential speed of the center of each ball 22 thus has two components: a tangential component, perpendicular to the axis of rotation of the shaft 30 and a longitudinal component parallel to the axis of the shaft 30 due to the pitch of the helix of the ball-race.
  • a ball 22 turns about an axis inclined with respect to the axis of the shaft 30 according to an angle equivalent to that of the helix of the ball-race. Moreover, the point of contact I between the ball 22 and the inner surface of the tube is always positioned on the line perpendicular to the axis of rotation passing through the point 0 . This results into the outer tube 20 being driven in translation at a speed proportional to the speed of rotation of the driving shaft 30 and to the pitch of the helical race.
  • the linear actuator of FIG. 1 can be mounted by carrying out the following steps:
  • FIG. 3 shows an example of a cam 40 used in the mounting of FIG. 1 .
  • the cam 40 has a cylindrical general shape. It includes a central bore 43 aimed at receiving the driving shaft 30 , as well as a key slot 44 formed from the bore 43 and aimed at allowing indexing the cam 40 on the shaft 30 .
  • a helical bevel 41 has been carried out by milling of a circular edge of the cam 40 .
  • This cam is formed from a cylindrical part with a straight cross-section, one circular edge of which is beveled, in order to form said helical cam surface inclined with respect to the axis of the cylindrical part, the ends of helical surface being connected by a setback surface with a conical general shape.
  • the milling operation is carried out using a conical cutter 100 the cutting edges of which form an angle of 45 degrees with respect to its axis of rotation 101 .
  • the cutter is mounted on a rotary machining spindle 102 .
  • a cylindrical rotation part 400 (shown in dotted lines) aimed at forming the cam 40 is mounted on a rotary table. It is so arranged with respect to the cutter 100 that their axes 101 and 401 are parallel and have a given separation e.
  • the part 400 is subjected during the milling operation to a rotational movement with respect to its axis 401 (indicated by arrow R).
  • the cutter 100 is subjected to a translational movement (indicated by arrow T) along its axis 101 .
  • the translational movement is carried out in a direction in which the cutter 100 moves away from the cylindrical part 400 .
  • the part 400 carries out a rotation of 360 degrees, while the spindle 102 is moved in translation by a distance equal to the pitch of the helical bevel to be generated. This milling operation leads to the generation of the helical bevel 41 oriented at 45 degrees with respect to the axis 401 .
  • the helical bevel of the cam 40 forms a circumferential surface 41 which widens when it is followed in the opposite direction to the milling and is connected at his ends by a setback with a conical shape 45 .
  • This setback with a conical shape is generated by the shape of the conical cutter when starting its initial radial passage in the part 400 .
  • the shape of the setback can vary according to the path of the initial passage of the cutter. If the conical cutter penetrates into the part 400 according to a tangential passage start, the setback obtained will have a planar general shape. If the conical cutter penetrates into the part 400 according to an oblique passage start, the setback obtained will have a planar general shape with conical connection.
  • the helical ball-race when the pitch of the race is large with respect to the diameter of the cams, the helical ball-race must be obtained by a different process.
  • a previous step of milling of the cylindrical part using a cylindrical cutter can be carried out, in order to obtain in the first place a helical surface oriented perpendicularly to the axis of the part.
  • a step of milling of the edge of the helical surface using a conical cutter is carried out, to make a helical bevel oriented at 45 degrees with respect to the axis of the part.
  • the helical bevel thus obtained forms a circumferential surface with a constant width which is connected at its ends by a conical setback.
  • FIG. 5 shows the positioning of two cams 40 and 50 with respect to each other on the driving shaft 30 .
  • Both cams 40 and 50 have each an identical beveled surface 41 , 51 . They are positioned side by side on the driving shaft 30 , so that their respective beveled surfaces 41 and 51 are faced to each other, in order to form a helical race for the balls 22 .
  • the cams 40 and 50 are each indexed on the shaft 30 by their key slot 44 or 54 .
  • the key slots 44 and 54 are so positioned with respect to the bore of the cams 40 and 50 that the conical setback surfaces 45 and 55 of the cams 40 and 50 are positioned in front of each other, in an opposite way, when the latter are mounted on the shaft 30 .
  • the conical setback surfaces 45 and 55 of both cams 40 and 50 advantageously form a widened zone 81 which accommodates the balls 22 and allows their re-circulation.
  • the shaft 30 of the actuator is rotated, the balls 22 roll on the ball race formed by the beveled surfaces 41 and 51 .
  • a ball 22 arrives in the re-circulation zone 81 where the two beveled surfaces 41 and 51 have a maximum width, it is no longer into contact with the inner surface 21 of the outer tube 20 , so that it does no longer roll.
  • the ball 22 remains in the re-circulation zone until it is pushed by the arrival of a next ball and thus automatically re-inserted into the ball-race.
  • the nut 70 formed by the association of the cams 40 , 50 , 60 has the advantage of not requiring the formation of an inner re-circulation race.
  • the balls 22 are automatically “recycled” as soon as they reach the re-circulation zone 81 connecting the ends of a ball-race.
  • FIG. 6 shows the positioning of the successive cams 40 , 50 and 60 with respect to each other on the driving shaft 30 .
  • These cams are so arranged that the re-circulation zones of the balls are not aligned.
  • the cams are oriented on the driving shaft 30 so that the re-circulation zones are angularly distributed in a regular way about the axis of the shaft 30 (axis of rotation and translation of the actuator).
  • the nut including two ball-races formed by the cams 40 , 50 and 50 , 60 , respectively, it has two re-circulation zones which are arranged at 180 degrees with respect to each other about the axis of the shaft 30 .
  • the cams In the case of a nut including three roll-races which would have three re-circulation zones, the cams would be so oriented that the re-circulation zones are arranged at 120 degrees with respect to each other about the axis of the shaft 30 .
  • the cams would be so oriented that the re-circulation zones are arranged at 360/N degrees with respect to each other about the axis of the shaft 30 .
  • This feature allows to avoid a rotational movement of the inner tube 10 with respect to the outer tube 20 which can occur when the actuator comprises only one pair of cams (i.e. only one ball-race) or when the re-circulation zones are arranged aligned.
  • the inner 10 and outer 20 tubes are made out of a relatively light material: for example, out of a composite or plastic material or out of a light alloy.
  • Ball-races can be formed on the inner surface 21 of the outer tube 20 . These ball-races allow to reduce the Hertz pressure exerted by the balls 22 on the surface of tube 20 .
  • the ball-races are formed by burnishing the inner surface 21 of the tube 20 .
  • the ball-races can advantageously be formed by the balls 22 themselves during the rotation of the shaft 30 .
  • the balls 22 produce a plastic distortion of the surface 21 while forming ball-races.
  • the constitution of the ball-races allows to apply compressive forces which a smooth cylindrical surface would not withstand.
  • these races allow to apparently increase the external friction coefficient between the ball and the tube.
  • the ball-races allow not to apply too great a prestressing force to the balls. Since the balls are guided by the ball-races, they cannot slide with respect to the outer tubular body 20 .
  • These ball-races have a helical pitch substantially equal to the helical pitch of the ball-race formed in the nut 70 .
  • the actuator includes, in combination, ball-races on interior surface 21 of the outer tube 20 and one nut 70 having re-circulation zones in the form of widened spaces. Thanks to this structure, when a ball arrives in a re-circulation zone, it penetrates radially towards the interior of the nut 70 , so that it is no longer into contact with one of the races formed in the outer tube 20 . Thus, when “recycled”, the ball passes from one ball-race onto an adjacent race, over a race edge, this passing over from one race to another one being possible thanks to the widened space forming the re-circulation zone.
  • the inner 10 and outer 20 tubes are also made out of a relatively light material.
  • Ball-races are formed on the inner surface of the outer tube 20 .
  • the ball-races are formed by a high-strength steel wire 91 positioned in a helical way inside the outer tube 20 .
  • the balls 22 roll resting on two successive windings of the wire 91 .
  • This variant allows to obtain a mechanically positive connection between the balls 22 and the races of the tube 20 (there is no longer any friction, but a support).
  • the longitudinal components of the forces of support on the windings of the wire 91 are positive supports.
  • the inner surface 21 of the outer tube 20 includes a helical groove 24 aimed at receiving the steel wire 91 .
  • This variant allows to use tubes made out of aluminum, KEVLAR ⁇ , carbon fibers or molded plastic, which guarantees the lightness of the final actuator structure obtained.
  • the inner surface 21 of the outer tube 20 is smooth.
  • Ball-races are formed on the inner surface of the outer tube 20 . They are formed by a first high-strength steel wire 91 positioned in a helical way inside the outer tube 20 and on which the balls 22 rest.
  • a second intercalated wire 92 having a diameter smaller than that of the first wire 91 extends between the windings of the first wire. This second wire 92 maintains the separation between the windings of the first wire. It prevents, in particular, the windings of the first wire 91 from separating during the passing through of a ball 22 . In a preferential way, the balls 22 are not into contact with the intermediate wire 92 .
  • This implementation is particularly simple and avoids having to use techniques for machining the outer tube 20 .
  • FIG. 10 shows still another variant of the invention in which ball-races are made by plastic distortion in a calibrated inner tube.
  • the inner tube 93 is arranged in the outer tube 20 and welded to the latter.
  • the ball-races in the inner tube 93 are made as follows.
  • a burnishing or shaping machine which includes a roller holder provided with three rollers arranged at 120 degrees with respect to each other and oriented according to the helix angle of the race to be obtained.
  • the inner tube 93 is fixed on a chuck the shape of which is close to the inner profile to be achieved.
  • the roller holder is rotated.
  • the tube 93 and the chuck are driven in translation.
  • the speed of translation of the tube 93 is set so that the translation distance is equal to the pitch of the helix at each turn of the roller holder.
  • the operation can be carried out in one single pass and the tube 93 is then highly cold hardened, which increases the rigidity and the hardness of the surface. Once shaped, the tube 93 is inserted into the outer tube 20 .
  • FIG. 11 shows a step of welding the inner tube 93 , in which the ball-races are formed, in the outer tube 20 of the actuator.
  • a spot welder including an inner thumb wheel 201 mounted on a shaft 203 and a motorized outer thumb wheel 202 .
  • the inner thumb wheel is inclined with respect to the shaft 203 according to an angle equal to the helix angle of the ball-races.
  • the welding operations are carried out on the bottom of the helical races into contact with the outer tube 20 .
  • the unit thus formed is boxed and the axial distortion of the unit is insignificant. This small distortion guarantees a linearity of the conversion of the rotational movement into a translational movement in the final actuator.
  • each cam 40 , 50 or 60 has a bevel oriented according to an angle smaller than or equal to 45 degrees with respect to the axis 401 of the cam, preferably strictly smaller than 45 degrees and preferably of about 35 degrees.
  • This feature allows to decrease the radial force which serves as a support for the reaction of the forces applied to the ball-race. Moreover, this feature facilitates the passing of the balls over the edges of the races during their re-circulation. Indeed, the component of the force which allows a ball to pass over a race edge (formed for example by a wire) passes above the edge of the race.
  • FIG. 12 shows a linear actuator of a telescopic type. This actuator is similar to that of FIG. 1 . It includes an inner tube 10 and an outer tube 20 the diameter of which is larger than the diameter of the inner tube 10 . The inner tube 10 extends partly in the outer tube 20 . It also includes a nut 70 comprised of a succession of cams 40 , 50 and 60 of cylindrical general shapes.
  • the linear actuator shown in FIG. 12 includes, in addition, a third tube 300 the diameter of which is larger than that of the outer tube 20 .
  • the outer tube extends partly in the third tube 300 .
  • the nut 370 is rigidly connected to the outer tube 20 , so that the outer tube 20 is capable of rotating a nut 370 including cams 340 and 350 .
  • the tubes 10 and 300 are locked in rotation with respect to each other and are capable of being driven to slide with respect to each other in their longitudinal direction.
  • the outer tube 20 is mounted floating, i.e. it is locked in rotation neither with respect to the inner tube 10 nor with respect to the third tube 300 .
  • the motor 2 of the actuator of FIG. 12 When the motor 2 of the actuator of FIG. 12 is operating, it rotates the nut 70 including the cams 40 , 50 and 60 . The balls 22 then roll between their ball-race and the inner surface of the intermediate tube 20 . Since the tubes 10 and 300 are locked in rotation with respect to each other, the rotation of the nut 70 causes the inner tube 10 to be displaced in translation with respect to the unit formed of the outer tube 20 and the third tube 300 . This translation is limited by a thrust.
  • the tubes 10 and 20 are then rotated simultaneously.
  • the outer tube 20 then rotates the nut 370 including the cams 340 and 350 .
  • the balls 22 then roll between their ball-race formed by the cams 340 and 350 and the inner surface of the third tube 300 . Since the tubes 10 and 300 are locked in rotation with respect to each other, the rotation of the nut 370 causes the unit comprised of the inner tube 10 and the outer tube 20 to be moved in translation with respect to the third tube 300 .
  • the unfolding can also occur at random depending on the friction torques occurring in the mechanism.
  • Such a telescopic actuator has the advantage of being able to reach larger unfolding lengths than with a simple actuator as shown in FIG. 1 .
  • the nut 70 includes two pairs of cams and the nut 370 includes only one pair of cams.
  • FIG. 13 shows the actuator of FIG. 12 in unfolded position.
  • the tubes 20 and 300 each have ball-races on their inner surfaces. These races preferably have the same pitch. Thus, the unfolding of the actuator will occur at a constant speed. In addition, it will be possible, by counting the number of revolutions of the motor, to know the exact position of the actuator.
  • the unfolding speed of the actuator will vary according to the tube which will be moving at a given moment.
  • a telescopic actuator including a plurality of tubes capable of being driven in translation with respect to each other, one can choose to establish different race pitches for the various tubes.
  • One thus obtains a telescopic actuator which sequentially unfolds with programmable values of motor/movement reduction coefficient over the total travel distance of the actuator. This feature allows to adapt the evolution of the motor torque provided depending on the profile of the load the actuator has been subjected to during its unfolding, this profile being determined length by length.
  • FIG. 14 shows a ball 22 with a center 0 maintained between the beveled surfaces 41 and 51 of the cams 40 and 50 and a ball-race formed, for example, by two wires 92 and 94 .
  • the points of contact between the ball 22 and the cam 40 , the cam 50 , the wire 92 and the wire 94 , are designated by B, D, C and A, respectively.
  • the angle between the plane P with a straight cross-section of the actuator passing through 0 and the straight line (OA) are designated by ⁇ 1 and the angle between the plane P and the straight line (OB) is designated by ⁇ 2 .
  • the forces exerted on the ball by the cams and the ball-race are designated by F A , F B , F C and F D .
  • the cams 40 and 50 are rotated so that the ball 22 arrives at a widened re-circulation zone as shown in FIG. 15 . From that moment on, the ball 22 is no longer into contact with the cam 50 , so that it is no longer balanced, since no force applies at D. The ball 22 is subjected to a force imparting it an acceleration allowing it to separate from the ball-race and to cross the wire 94 , in order to position itself on the adjacent race.
  • the passing over of the ball 22 from one race to the next one can occur only if ⁇ 1 ⁇ 2 , so that the resultant of the forces on the ball passes over the wire 94 .
  • ⁇ 2 can be chosen between 50 and 60 degrees, preferably to be 55 degrees.
  • the cam 40 has a helical beveled surface 41 oriented at 35 degrees with respect to the plane P.
  • a cam having such a helical bevel can be achieved by machining a cylindrical part with a conical cutter having at the top half an angle of 55 degrees.
  • FIG. 16 shows the positioning of two cams 40 and 50 with respect to each other.
  • the plane Q extends transversely to the plane of the diagram and passes through the axis of rotation of the nut 70 including both cams 40 and 50 .
  • the cams 40 and 50 are identical. They are arranged in front of each other, so that the rolling surfaces 41 and 51 face each other.
  • the cams are indexed by their key slots (see FIG. 5 ), the key slots extending in the plane Q.
  • the key slots are positioned so as to form an angle ⁇ with respect to the reference mark formed by an end of the helical surface corresponding to the leading plane of the cutter.
  • the angle ⁇ can be set in order to minimize the space of evolving of the balls in the re-circulation zone 81 , in order to avoid the presence of several balls at the same time in this zone and to keep the largest possible number of “working” balls.
  • the setting of the angle ⁇ depends namely on the pitch of the ball-race, on the orientation of cam surfaces 41 and 51 , on the diameter of the balls 22 , on the diameter of the wires 92 and 94 used for making the races.
  • a way for determining this angle ⁇ consists in determining the volumes in which the center O of a ball moves when the latter is resting against one of the cam surfaces, resting on the other cam surface and resting on the ball-races, respectively.
  • the intersection of these volumes represents the space in which the ball is guided.
  • This space can be modified by varying the angle ⁇ .
  • the space of intersection must both be large enough for a ball to be able to enter into the re-circulation zone and to move on the helical ball-race and sufficiently restricted to prevent several balls from being present simultaneously in the re-circulation zone 81 .
  • the shape of the space obtained depends on angle ⁇ and also on the shape of the setback surfaces of the cams.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Transmission Devices (AREA)
US10/524,298 2002-08-29 2003-08-29 Mechanical actuator including a helical-cam nut Abandoned US20050268736A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR02/10715 2002-08-29
FR0210715A FR2844019A1 (fr) 2002-08-29 2002-08-29 Actionneur mecanique a friction comprenant un ecrou interne a billes dans lequel les billes sont montees avec precontrai nte
PCT/FR2003/002607 WO2004020871A2 (fr) 2002-08-29 2003-08-29 Actionneur mecanique incluant un ecrou a cames helicoidales

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US (1) US20050268736A1 (de)
EP (1) EP1523630B2 (de)
AU (1) AU2003278225A1 (de)
DE (1) DE60303610T3 (de)
ES (1) ES2258734T5 (de)
FR (1) FR2844019A1 (de)
WO (1) WO2004020871A2 (de)

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US20070175099A1 (en) * 2005-12-07 2007-08-02 Brose Schliesssysteme Gmbh & Co. Kg Drive arrangement for motorized movement of a motor vehicle door or the like
US20090095098A1 (en) * 2007-10-10 2009-04-16 Parker-Hannifin Corporation High force electro-mechanical actuator
US20100000354A1 (en) * 2008-01-15 2010-01-07 Jtekt Corporation Ball screw unit
US20110174101A1 (en) * 2010-01-18 2011-07-21 Suspa Gmbh Height-adjustable actuation device
US20110276202A1 (en) * 2010-05-07 2011-11-10 Eurocopter Simplified flight control system including a declutchable friction device
US20120011951A1 (en) * 2008-11-25 2012-01-19 Precilec Linear actuator
US20120024092A1 (en) * 2010-06-21 2012-02-02 Brose Schliesssysteme Gmbh & Co. Kg Spindle drive for the motorized adjustment of an adjustment element of a motor vehicle
US20130206020A1 (en) * 2010-05-17 2013-08-15 Iacobucci Hf Electronics S.P.A. Single-column trash compactor
WO2013149806A1 (de) * 2012-04-03 2013-10-10 Schaeffler Technologies AG & Co. KG Betätigungsvorrichtung für eine kupplung
CN103388632A (zh) * 2012-05-11 2013-11-13 舍弗勒技术股份两合公司 用于运行用于离合器的操纵装置的方法和用于离合器的操纵装置
US20140150580A1 (en) * 2012-12-01 2014-06-05 John McEntee Rotary to linear transmission
DE102017127937A1 (de) * 2017-11-27 2019-05-29 Logicdata Electronic & Software Entwicklungs Gmbh Teleskopierbarer Linearaktuator und höhenverstellbarer Tisch
US20200316499A1 (en) * 2017-10-18 2020-10-08 Metso Sweden Ab Filter press and method for separating the solid components from the liquid components of a slurry
DE102022120145A1 (de) 2022-08-10 2024-02-15 Schaeffler Technologies AG & Co. KG Planetenwälzgewindetrieb

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FR2888277B1 (fr) * 2005-07-08 2007-09-07 Bubendorff Sa Dispositif d'entrainement pour systeme de fermeture de batiment
DE102013016769A1 (de) * 2013-10-09 2015-04-09 Kuka Laboratories Gmbh Instrumentenanordnung

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US4138902A (en) * 1976-11-19 1979-02-13 Roltra S.P.A. Screw-nut screw transmission coupling with ball circulation
US5358265A (en) * 1990-08-13 1994-10-25 Yaple Winfred E Motorcycle lift stand and actuator
US5636549A (en) * 1993-12-22 1997-06-10 Hughes Electronics Wire wound threaded elements including lead screws, roller not assemblies and process
US6101889A (en) * 1998-01-20 2000-08-15 Thomson Saginaw Ball Screw Company, Llc Ball screw and nut linear actuator assemblies and methods of constructing and operating them
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Cited By (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070175099A1 (en) * 2005-12-07 2007-08-02 Brose Schliesssysteme Gmbh & Co. Kg Drive arrangement for motorized movement of a motor vehicle door or the like
US20090095098A1 (en) * 2007-10-10 2009-04-16 Parker-Hannifin Corporation High force electro-mechanical actuator
US8001861B2 (en) * 2007-10-10 2011-08-23 Parker-Hannifin Corporation High force electro-mechanical actuator
US20120125134A1 (en) * 2008-01-15 2012-05-24 Jtekt Corporation Ball screw unit
US20100000354A1 (en) * 2008-01-15 2010-01-07 Jtekt Corporation Ball screw unit
US8424401B2 (en) * 2008-01-15 2013-04-23 Jtekt Corporation Ball screw unit
US8230749B2 (en) * 2008-01-15 2012-07-31 Jtekt Corporation Ball screw unit
US20120011951A1 (en) * 2008-11-25 2012-01-19 Precilec Linear actuator
RU2509935C2 (ru) * 2008-11-25 2014-03-20 Пресилек Линейный приводной механизм
DE102010000970C5 (de) 2010-01-18 2022-10-13 Suspa Gmbh Höhenverstellbare Betätigungs-Einrichtung
US8635922B2 (en) * 2010-01-18 2014-01-28 Suspa Gmbh Height-adjustable actuation device
US20110174101A1 (en) * 2010-01-18 2011-07-21 Suspa Gmbh Height-adjustable actuation device
US20110276202A1 (en) * 2010-05-07 2011-11-10 Eurocopter Simplified flight control system including a declutchable friction device
US8886370B2 (en) * 2010-05-07 2014-11-11 Airbus Helicopters Simplified flight control system including a declutchable friction device
US9221600B2 (en) * 2010-05-17 2015-12-29 Iacobucci Hf Aerospace S.P.A. Single-column trash compactor
US20130206020A1 (en) * 2010-05-17 2013-08-15 Iacobucci Hf Electronics S.P.A. Single-column trash compactor
US9255436B2 (en) * 2010-06-21 2016-02-09 Brose Schliesssysteme Gmbh & Co. Kg Spindle drive for the motorized adjustment of an adjustment element of a motor vehicle
US20120024092A1 (en) * 2010-06-21 2012-02-02 Brose Schliesssysteme Gmbh & Co. Kg Spindle drive for the motorized adjustment of an adjustment element of a motor vehicle
WO2013149806A1 (de) * 2012-04-03 2013-10-10 Schaeffler Technologies AG & Co. KG Betätigungsvorrichtung für eine kupplung
CN103388632A (zh) * 2012-05-11 2013-11-13 舍弗勒技术股份两合公司 用于运行用于离合器的操纵装置的方法和用于离合器的操纵装置
US20140150580A1 (en) * 2012-12-01 2014-06-05 John McEntee Rotary to linear transmission
US20200316499A1 (en) * 2017-10-18 2020-10-08 Metso Sweden Ab Filter press and method for separating the solid components from the liquid components of a slurry
US11833453B2 (en) * 2017-10-18 2023-12-05 Metso Sweden Ab Filter press and method for separating the solid components from the liquid components of a slurry
DE102017127937A1 (de) * 2017-11-27 2019-05-29 Logicdata Electronic & Software Entwicklungs Gmbh Teleskopierbarer Linearaktuator und höhenverstellbarer Tisch
DE102022120145A1 (de) 2022-08-10 2024-02-15 Schaeffler Technologies AG & Co. KG Planetenwälzgewindetrieb
DE102022120145B4 (de) 2022-08-10 2024-06-06 Schaeffler Technologies AG & Co. KG Planetenwälzgewindetrieb

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WO2004020871A3 (fr) 2004-07-01
ES2258734T5 (es) 2012-01-02
EP1523630B8 (de) 2006-06-28
EP1523630B2 (de) 2011-08-10
EP1523630B1 (de) 2006-02-15
ES2258734T3 (es) 2006-09-01
AU2003278225A1 (en) 2004-03-19
FR2844019A1 (fr) 2004-03-05
DE60303610T2 (de) 2006-10-19
DE60303610T3 (de) 2012-01-26
EP1523630A2 (de) 2005-04-20
WO2004020871A2 (fr) 2004-03-11
DE60303610D1 (de) 2006-04-20

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